U.S. Pat. No. 4,983,422 to Davis et al., Jan. 8, 1991, discloses a ceramic composite with a low dielectric constant and high mechanical strength. The composite is made from a liquid aluminum oxide precursor and a reinforcement fabric. The method for producing the ceramic composite comprises introducing the precursor into a reinforcement fabric, curing the precursor to set the desired geometry, and converting the cured precursor to an aluminum oxide ceramic by pyrolysis.
U.S. Pat. No. 5,198,302 to Chyung et al., Mar. 30, 1993, discloses a fiber reinforced ceramic matrix composite formed from a preform comprising silicon nitride fibers coated with boron nitride and alumina and a matrix material. When the preform is heated in an oxidizing atmosphere essentially free of water vapor, a composite with low dielectric loss and high strength is produced.
U.S. Pat. No. 5,318,930 to Leung et al., Jun. 7, 1994, discloses a fiber reinforced silicon carboxide composite with adjustable dielectric properties. The dielectric constants of the composites are adjusted by varying the reinforcing fibers and the carbon content of the black glass matrix.
U.S. Pat. No. 5,601,674 to Szweda et al., Feb. 11, 1997, discloses a method or making a fiber reinforced ceramic matrix composite that is oxidation stable. The method comprises heating a matrix mixture slurry interspersed about reinforcing fiber in an oxidizing atmosphere to yield a crystalline ceramic phase.
However, all of these composites contain oxide matrix materials, which suffer from the drawback of insufficient capability to retain mechanical strength at high process temperatures. One object of this invention is to provide a ceramic matrix composite that can withstand repeated exposure to high process temperatures (greater than 1,000.degree. C.). A further object of this invention is to provide a ceramic matrix composite with low dielectric constant and loss factor, high mechanical strength, low observability, and low oxidation at high working temperatures in air.